In CPV modules, the incident light, in particular, the solar radiation, is concentrated on a photovoltaic cell by an optical system comprising, e.g., a mirror or a lens, such as a Fresnel lens or a spherical lens. The cell is thereby positioned at the focus of the lens. Commonly, such CPV modules are mounted, alone or combined in arrays, on tracking units in order to be optimally oriented toward the incident light, in particular, following the brightest region in the sky. Preferably, CPV modules should be sealed completely to avoid degrading of the solar cells and other electrical components, e.g., the bypass diodes or the electrical wiring, due to environmental influences. In particular, an elevated level of relative humidity in the module, which can cause, under certain circumstances, condensation of water vapor on the components situated inside the module.
Several prior art approaches for resolving the problem of condensation and humidity inside a solar module are known. A first approach is based on a completely sealed solar module. Prior art document WO 2011/085086 A2 discloses an entirely sealed solar module in which the solar module is connected to an expansion bag accommodating for the pressure changes inside a solar module during thermal cycling. Optionally, a supplemental desiccant unit is installed to remove moisture that has penetrated into the sealed module. This approach is not well adapted to large CPV modules and plants, due to the huge dimensioning of the expansion bag.
In another approach, disclosed in prior art document WO 2009/146842 A1, an adsorber or desiccant unit is connected to the module, whose role is to dry the incoming air. Adsorption is a phenomenon leading to the physico-chemical fixation of molecules of water vapor on the surface of a solid, in particular, an adsorber or desiccant material, such as, for instance, a silica gel that is characterized by a high porosity. Moist air from outside the module is blown with a fan through the adsorber unit, in particular, containing a silica gel as an adsorber material, which absorbs excess moisture, and dried air is sent directly to the CPV modules. However, with time, the adsorbent becomes saturated and must be regenerated to remove moisture. This regeneration generally takes place when the relative humidity measured after the adsorbent unit is above a certain limit, and the regeneration duration depends on this relative humidity level. This regeneration is ensured by the passage of air heated to a temperature above 60° C. and the moist hot air has to be evacuated outside.
This regeneration phase is highly energy consuming and needs an active device assuring the flow of air, in particular, a fan. Moreover, lack of supervisory control and communication leads to an unnecessary use of the drying unit, even when the outside meteorological conditions are optimal in avoiding dry modules, in particular, elevated outside temperature and low relative humidity outside the module.